This invention relates to transition code processing systems and more particularly, to an optical reader for generating signals representing information stored in the form of black and white coded bars.
In present-day data processing systems, the use of bar code symbols on labels or articles as a means for acquiring data at a point of sale is wellknown. In reading these bar code labels, it is necessary to provide a clock pulse or other type of synchronizing signal in order that the information be properly entered from the sensing device to the utilization device. It is further necessary to provide an accurate time relationship between the movement of the sensing device with respect to the bar code symbols and the clock pulse in order for the information received to be accurately decoded. To meet these requirements, prior bar code recognition systems such as disclosed in U.S. Pat. Nos. 2,952,008 and 3,409,760 provide a separate clock or timing symbol adjacent the bar code symbol, both symbols being sensed simultaneously. Such an arrangement provides the clock pulses which bear a direct relationship to the information to be sensed. However, the requirement for controlled movement of the sensing device with respect to the bar code symbols is still important. When the movement between the sensing device and the bar code symbols was intermittent, the arrangement of prior bar code symbols and their associated sensing members was found inadequate to functionally operate under this intermittent condition. It is therefore the primary object of this invention to provide an optical sensing means for reading a unique coding arrangement in which a plurality of coded symbols are capable of producing information independent of the speed of movement of the coded symbols past the sensing device while still being selfclocking. It is a further object of this invention to provide an optical sensing means which is inexpensive to manufacture and simple in construction.